Retaining walls are widely used in a variety of landscaping applications. Typically, they are used to maximize or create level areas and also to reduce erosion and slumping. They may also be used in a purely decorative manner. In the past, retaining wall construction was labor intensive and often required the skills of trained tradespeople such as masons and carpenters. More recently, retaining wall construction has become significantly simplified with the introduction of self-aligning, modular, molded blocks of concrete that may be stacked in courses without the use of mortar or extensive training. With these types of blocks, it is possible to erect a retaining wall quickly and economically, and the finished product creates the impression and appearance of a conventional block and mortar retaining wall. The feature that allows such blocks to be so easily and precisely assembled is the interconnection between adjacent courses of blocks. Typically, each block will include a projection and a recess located at oppositely facing surfaces, such as a top surface and a bottom surface, for example. The projection and recess are complimentarily shaped, with the projection protruding beyond the bottom surface of the block and with the recess extending inwardly from the top surface of the block. In use, a projection of a first block is received within the recess of a second block to interconnect and position the blocks adjacent each other in a predetermined relation. With a plurality of blocks, such interconnections make it possible to lay courses of blocks in an accurate and expedient manner. Moreover, such an assembled retaining wall is able to resist lateral forces exerted by the material being retained and reduce bowing. Blocks having these interconnections are usually the same size and may be assembled in a coplanar arrangement in only a simple, running bond pattern. In a variation of the aforementioned blocks, the projection and recess may be arranged so that adjacent courses are offset a predetermined amount. With this type of block, each successive course may be offset from the preceding course by the same amount so that the assembled wall is skewed at a predetermined angle from the vertical. These blocks also have the same dimensions to enable them to set in only a simple, running bond pattern.
A recent development in mortarless retaining walls has been the advent of blended pattern retaining walls. These walls differ from the aforementioned walls in that the preformed blocks used to construct a retaining wall are differently sized. This feature allows retaining walls to be assembled in a variety of patterns and bonds. Usually, these types of preformed blocks are horizontally and vertically oriented and have dimensions that are based upon an incremental unit such as the thickness of a horizontal, preformed block. For example, the thickness of a horizontal block is one increment and the height of a vertical block is two increments. With these types of preformed blocks, it is possible to construct a retaining wall with no discernable courses. A drawback with such a retaining wall is that setbacks are not possible and the assembled retaining wall must be substantially vertical. Alternatively, a retaining wall may be arranged in thick courses, and the blocks within these thick courses may be randomly arranged. For example, a course may be two incremental units high within which the differently dimensioned preformed blocks are arranged. Or, the course may be three incremental units high within which the differently dimensioned preformed blocks are arranged. There are several drawbacks with this type of wall. One drawback is that the vertical blocks dictate the height of the course. Thus, if vertical blocks are used, each entire course must be coplanar and all of the blocks must lie in the same plane. Otherwise, the projections of blocks in one course would not be able to be received within the recesses in blocks of another course, and the interconnection would be defeated. Another drawback with such this type of wall is that the number of arrangements available within each course is limited, and a truly random arrangement is not possible.